There have been suggested various types of a driving control device of an opening and closing body for a vehicle. For example, a driving control device of an opening and closing body disclosed in Japanese Patent No. 3411383 (Reference 1) controls driving of a motor so as to perform insertion avoidance processing which stops and reverses driving of the motor, when a foreign member is inserted during the ascending and descending operation of a door glass used as the opening and closing body, by a driving force of a DC motor. The driving control device includes a number of revolutions detection section which detects a number of revolutions of the motor, a rotation torque difference calculation section which calculates a rotation torque difference applied to the DC motor from the number of revolutions difference of the DC motor between a non-load state and a load state, detected by the number of revolutions detection section, a determination section which determines whether a predetermined rotation torque difference is generated in the rotation torque difference calculation section, and an instruction section which instructs execution of the insertion avoidance processing when the determination section determines that the predetermined rotation torque difference is generated. In this case, in the determination of a decreasing degree of the number of revolutions of the DC motor for the insertion determination of the foreign member, the number of revolutions is not compared to a predetermined threshold value which is found empirically or experimentally, but torque (rotation torque difference) which is applied to the DC motor when the foreign member is actually inserted is directly acquired by the calculation. Therefore, it is possible to determine the insertion of the foreign member regardless of the assembly state or the like.
Furthermore, a driving control device of an opening and closing body disclosed in JP 2010-248884A (Reference 2) detects the insertion of the foreign member based on a relationship between a rotation speed difference and a threshold value. The rotation speed difference here is a deviation between a rotation speed of the motor in an idling section for a closing driving from a door-half open state of a hack door as the opening and closing body to a fully-closed state thereof and a current rotation speed detected thereafter. Reference 2 also discloses that detection sensitivity of the insertion is changed by varying the threshold value based on a temperature which is assumed from the rotation speed of the motor in the idling section, thereby it is possible to suppress the influence of the temperature characteristics of the motor and more suitably detect the insertion of the foreign member.
FIG. 11 is a graph which illustrates a relationship between a stroke (rotation amount) St of the motor in relation to the opening and closing position of the back door when starting the driving of the motor at the transition of the back door into a door-half open state as a starting point to drive the back door in the closed state, and a rotation speed difference DN. In FIG. 11, the temperature correction of the threshold value is omitted for simplification. As mentioned above, the idling section is set in the motor, a state just before a stroke Sto of the motor when the idling section is finished is considered as a non-load state, and the rotation speed difference DN of that time is set to zero. Moreover, as illustrated by a broken line in FIG. 11, a rotation speed difference DN, (hereinafter, referred to as “standard rotation speed difference”) anticipated to correspond to the stroke Sto, decreases in a step manner just after the stroke Sto where the idling section is finished, and monotonously and continuously decreases until a stroke Ste of the motor where the transition of the back door into the fully-closed state is completed. This is due to the fact that a load is generated just after the stroke Sto to rapidly reduce the rotation speed of the motor, and door reactive force (for example, elasticity of a weather strip which seals the back door in a liquid-tight manner) which becomes a load according to the closing operation of the back door as an increase in stroke St is continuously increased, so that the rotation speed of the motor is continuously reduced. It is needless to say that the standard rotation speed difference becomes a negative number in the entire range of the strokes Sto to Ste.
Moreover, a detection threshold value Th for the insertion detection is calculated according to the following formula based on the standard rotation speed difference illustrated by the broken line.Th=“standard rotation speed difference”−Z 
Herein, Z is an insertion determination torque, and is set to a predetermined value (a positive number) based on a rotation speed difference corresponding to a load when the insertion occurs.
Thus, the detection threshold value Th is a value (a negative number) which is further reduced than the standard rotation speed difference illustrated by the broken line, by an insertion determination torque Z. Thereby, the detection threshold value Th is set considering the door reactive force or the like, and an erroneous detection of the insertion is suppressed. Moreover, when it is determined that the actual rotation speed difference DN is lower than the detection threshold value Th, it is considered that a load corresponding to the insertion occurrence is generated, and thus predetermined insertion handling processing (stop and inversion of the motor or the like) is performed.
FIG. 11 also illustrates a transition of the rotation speed difference DN by a bold solid line when the insertion occurs. As illustrated in FIG. 11, a stroke Sth at which the rotation speed difference DN becomes lower than the detection threshold value Th is a detection timing of the insertion.
In the meantime, a stroke Ste corresponding to the fully-closed state of the back door illustrated in FIG. 11 would have a deviation in a predetermined range shown with a dot pattern. That is, the stroke Ste possibly takes from a stroke Ste1 where the stroke St is the smallest to a stroke Ste2 where the stroke St is the largest in the range. This is due to the fact that a relationship between the stroke St of the motor and the opening and closing position of the back door is not uniform due to assembling variation or the like.
Thus, for example, when the transition of the back door to the fully-closed state in the stroke Ste1 is completed, the range of the stroke Ste1 to Ste2 becomes an over-stroke region where the insertion cannot occur. However, even when the transition of the back door to the fully-closed state in the stroke Ste2 is completed, there is a need for the detection of the insertion with a suitable sensitivity. Therefore, if a suitable detection threshold value Th is expressed by a fully-closed state threshold value Thc at the fully-closed state of the back door, the detection threshold value Th needs to be set to become the fully-closed state threshold value Thc at the stroke Ste2.
For this reason, when the transition of the back door to the fully-closed state is completed in a stroke St which is smaller than the stroke Ste2, the detection threshold value Th in that stroke St (and in the proximity thereof) is increased more than the appropriate fully-closed state threshold value Thc. That is, the rotation speed difference DN is more easily lowered than the detection threshold value Th, and the insertion may be erroneously detected.
A need thus exists for a driving control device of an opening and closing body for a vehicle, which is capable of suppressing the erroneous detection of insertion at least in the fully-closed state or in the proximity thereof when driving the opening and closing body into the closed state.